In response to the ever increasing concern over environmental contamination and the human and ecological consequences, this proposal suggest developing ultratrace analytical methods for some of the substances of concern with wide applicability to many environmental and biological samples. The approach as outline herein will be to focus on organoarsenicals, organotins, inorganic arsenic, and organic compounds containing halogens and/or phosphorus. Pg to sub-pg levels of detection will be developed form the perspective that total amounts of element, while useful, do not provide sufficient information and therefore speciation is necessary. Methods for speciation will utilize gas chromatography or high performance liquid chromatography as is most appropriate. The method detection will be plasma source mass spectrometry. Both GC and HPLC enjoy tremendous popularity for separation of complex and difficult samples. To date, the most popular method of operation has been to use group sensitive detectors such as electron capture and ultraviolet absorption rather than element specific detection. However, with element specificity the ability to determine elemental ratios and potentially empirical formulae at trace levels are strong driving forces for implementation of these detectors. Multielement chromatograms result if several elements are monitored, thereby minimizing possible chromatographic ambiguities from lack of resolution or separation. Atomic spectrometry is recognized for its element specificity and low detection limits. Plasma source mass spectrometry further enhances this by allowing detection at the part-per-trillion levels and the ability to monitor several elements in a chromatographically separated compound. To date, there have been only few exploratory reports which have utilized plasma MS for chromatographic detection. Excellent low level detection has been attained in our initial studies. This proposal suggest further development of this early work with the expectation of improving detection levels and includes use of helium plasmas and mixed gas he/Ar plasmas for more efficient ion formation with nonmetals. It also includes applications to the environmentally and biologically significant compounds as mentioned above by utilizing a variety of complex sample types. Furthermore, isotope ratio information may help identify the contamination source.